This invention relates to an apparatus for the lasting of shoe uppers and/or shoes onto shoe lasts, especially shoes to be repaired, and for removing completed shoes from the lasts.
In the production of shoes, soles of polyurethane, thermoplasts, Nylon, etc. material are injection molded in place employing a shoe-soling machine having several work stations. Before applying the soles, the shoe or boot uppers are pulled onto the shoe lasts, so that, together with extrusion molds, the material is injection molded for applying the soles. Generally, the work stations include height-adjustable rotatable heads at which the lasts carrying the shoe uppers are arranged in pairs, so that, during the operation at the work station, a sole can be applied to one shoe upper, while simultaneously a completed shoe or boot can be removed from the last at a different, mold-opening work station.
Also, glue presses may be employed for gluing soles onto the lasted shoe uppers. Such is the normal method for soling worn shoes.
Initially, the shoe material is normally formed into shoe uppers by placing the material onto clamping lasts away from the shoe soling work station. In many cases, the formed shoe uppers are removed from the lasts and are thereafter pulled onto the metal lasts at the shoe soling machine.
It is also known to injection mold the soles directly onto the shoe uppers formed on the clamping lasts at the shoe forming station. Thus, the clamping lasts are removably mounted on last holders. Such last holders, being separate parts, provide the connection with the rotatable heads. These shoe lasts may therefore be formed similar to that of a shoe last on which the shoe upper itself is formed. In general, these clamping lasts are so arranged as to be of a somewhat higher elevation than that of the shoe upper so that, after the lasting of the shoe upper, the last can be connected with the last holder without difficulty. Otherwise, if the shoe uppers are elevated relative to the lasts, the height difference can, in certain circumstances, be equalized by suitable spacers. The forming of a shoe or boot upper on a last which is thereafter pulled onto a metal last for shoe soling, or the lasting on a clamping last at the shoe upper forming station, always proceeds in such a manner that the shoe leather or other material, which has previously been dampened, is formed on the last or clamping last, and thereafter when removed to the metal last, the sole is applied, and the finished shoe is passed through a heating station so that it retains its requisite shape after removal from the last.
Basically, the same problems arise during lasting, changing of lasts and removal from lasts, if the last or clamping last is formed of a single piece, such that the shoe material will be stretched during lasting, while changing lasts or during removal from the last. During such operation, the shoe material could permanently deform thereby changing the intended shoe size. Basically, this problem is avoided by providing lasts or clamping lasts of two parts so that, during lasting, changing of lasts or removal from the last by means of a relative movement of these two parts toward one another, the movement of the foot (as when normally putting on or removing a shoe) can essentially be reproduced so as to avoid wrenching the shoe.
German Pat. No. 16 85 389 generally discloses a two-part last comprising a heel part and a front toe part which basically serves the purpose of permitting boots to be lasted or removed from the lasts without affecting the shoe size during formation of the shoe uppers.
Similar problems are prevelant during a shoe repair operation, especially when gluing on new shoe soles. Heretofore, single part lasts have always been employed for original soling or repairing of even customized shoes in shoe repair shops, etc. However, the shoes are often widened by the use of such single part lasts as when they are pulled tightly onto the last. This is also true during the production of shoes or boots when the soles are glued on.
Despite the advantages obtained with the use of two-part lasts and/or clamping lasts, it is recognized that dealing with these two-part lasts is cumbersome, and that to some extent continued stretching of the shoe material cannot be entirely avoided.